tools: add copy functionality
tools: add copy functionality

sloffs can now copy a SLOF flash image from one file to
another. This is especially useful when the input is not
a regular file, but the slof_flash device. The -c, --copy
parameter copies only the actual SLOF flash image instead
of the whole device. This should result in a file, which
is identical to the file from the SLOF build process.

(cherry picked from commit 587eb035ac1fb17c3b8ab236bb06e793f08bb3ea)

Cherry picked from https://lisas.de/~adrian/slof/slof.git/

Signed-off-by: Adrian Reber <a1b909ec1cc11cce40c28d3640eab600e582f833@lisas.de>
Signed-off-by: Alexey Kardashevskiy <ac1fc56530d7d037e1ea666f130daca22d72f964@ozlabs.ru>

aik/SLOF,stefanberger/SLOF-tpm,qemu/SLOF,open-power-host-os/slof,stefanberger/SLOF-tpm,open-power-host-os/slof,aik/SLOF,open-power-host-os/slof,stefanberger/SLOF-tpm,aik/SLOF,qemu/SLOF,qemu/SLOF,open-power-host-os/slof